Ember Page Title Flash Update

controllers.application\.js

import Controller from '@ember/controller';
import { tracked } from '@glimmer/tracking';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';

  @tracked
  messageCount = 0;

  constructor() {
     super(...arguments);
     setInterval(() => {
       if (this.messageCount > 1) {
     			this.messageCount = 0;
       } else {
         this.messageCount = 2;
       }
     }, 1000);
  }
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
{{#if this.messageCount}}
	{{page-title "(" this.messageCount ")" " - " "Flash Message"}}
{{else}}
	{{page-title "Flash Message"}}
{{/if}}
<p>Check rendered twiddle iFrame title in dev tools</p>
<p>Message count: {{this.messageCount}}</p>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0",
    "ember-page-title": "6.2.1"
  }
}